Effects of exercise on l-carnitine and lipid metabolism in African catfish (Clarias gariepinus) fed different dietary l-carnitine and lipid levels

Abstract

African catfish (Clarias gariepinus) were fed four isonitrogenous diets (34% crude protein), each containing one of two lipid (100 or 180g/kg) and two l-carnitine (15 or 1000mg/kg) levels. After 81d of feeding, thirty-two fish (body weight 32g) from each dietary group were randomly selected, sixteen fish were induced to a 3-h swim (speed of 15body length (BL)/s), while the other sixteen fish were kept under resting condition. Fish fed 1000mg l-carnitine accumulated 35 and 5times more l-carnitine in plasma and muscle, respectively, than fish fed the 15mg l-carnitine. Muscle l-carnitine content was significantly lower in exercised fish than in rested fish. High dietary lipid level (fish oil) led to an increase in muscle n-3 PUFA content and a decrease in SFA and MUFA content. In liver, the increase in dietary lipid level resulted in an increased levels of both n-6 and n-3 PUFA. l-carnitine supplementation significantly decreased n-3 PUFA content. Exercise decreased n-3 PUFA in both muscle and liver. Plasma lactate and lactate dehydrogenase, normally associated with increased glycolytic processes, were positively correlated with exercise and inversely correlated with dietary l-carnitine level. l-carnitine supplementation reduced significantly the RQ from 072 to 063, and an interaction between dietary l-carnitine and lipid was observed (P<003). Our results indicate that an increase in fatty acids (FA) intake may promote FA oxidation, and both carnitine and exercise might influence the regulation of FA oxidation selectivity. Copyright © The Authors 2009.